The present invention relates to an airbag installed on a motor vehicle such as an automobile and an airbag device provided with such an airbag.
An airbag device generally includes an airbag for receiving a body of an occupant and a gas generator housed in the airbag for releasing gas to inflate the airbag. According to one of the methods for manufacturing an airbag for use in such an airbag device, an airbag is formed as a bag by subjecting a sheet-shaped web to a combination of folding and sewing (see, for example, Patent Document 1: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 8-506296)
A conventional airbag described above is constructed as a bag prepared by folding a sheet-shaped web cut into a predetermined shape along a predetermined folding line and finally sewing free edges with each another. A circumferential sewing such as sewing free edges with each other is an important process that particularly affects the air-tightness and strength of an airbag, and has a significant effect on the inflation/deployment performance and the restraint performance of the airbag. Accordingly, a circumferential sewing process for free edges includes a sewing process for a long sewing section, as compared to other supplemental sewing such as an installation of a reinforcement cloth or the like, accounting for a relatively large part of airbag manufacturing cost. For these reasons, there is a need for an airbag to reduce the manufacturing cost.
An object of the present invention is to provide an airbag and an airbag device having the airbag so as to significantly reduce the manufacturing cost by eliminating the need for the circumferential sewing process.
Further objects and advantages of the invention will be apparent from the following description of the invention.